Yes it can happen, especially if you have a short cycle, because ovulation may come soon after periods. Sperm can also survive a few days. So dont assume right after periods is totally safe.
With irregular cycles like mine, ovulation timing is really unpredictable, so i wouldnt rule it out. I never relied on the calendar method myself. If you are unsure, better to talk to your gynac about your cycle.
I was reading about this too. Apparently the fertile window can shift depending on cycle length. So just after periods isnt always a free zone, interesting na.
